Medical sonography is a diagnostic medical imaging method used for the visualization of soft tissue, such as muscles, tendons and internal organs. This type of technology is commonly understood to be safer, less expensive and more portable compared to other diagnostic imaging techniques, such as magnetic resonance imaging (MRI) or computed tomography (CT).
Compared to other prominent methods of medical imaging, ultrasonography (ultrasound) has several advantages. Unlike other imaging techniques, ionizing radiation is not a component of sonography and so poses no known risks to the patient. In addition, it provides images in real-time (rather than after an acquisition or processing delay), it is portable and can be brought to a patient's bedside, and it is substantially lower in cost. Drawbacks of ultrasonography include various limits on its field of view including difficulty imaging structures behind bone, and its relative dependence on a skilled operator. Ultrasound is also increasingly being used in trauma and by EMT response teams.
The non-invasive and portable nature of an ultrasound exam provides immediate results that are nearly as informative as other imaging exam methods. Further, ultrasound guided needle placement has allowed clinicians to perfect regional anesthesia procedures, needle biopsies, central line placement, and other procedures. Injections of cortisone, platelet rich plasma, hyaluronic acid supplements and local anesthetics provide pain relief and healing benefits through accurately place injections.
Using ultrasound to view a needle to accurately place an injection greatly increases the rate of successful placement of the medicament. Though a variety of techniques are used to track the path of the needle, from mechanical to magnetic, most require specialized probes and needles, the placing of markers, calibration, and a certain amount of pre-procedure setup. Finding a needle tip during an ultrasound procedure can be technically challenging and this is particularly true with out of plane needle insertion techniques in which the needle is inserted into the patient outside of the plane of the ultrasound transducer (probe). When a needle is inserted out of plane with the transducer (probe), there are a number of reasons that the needle image is not seen. For example, the needle image may not be seen because: (1) the transducer is still far away from the needle and thus, the beam from the transducer (probe) is not crossing the needle or (2) the beam hitting the needle is deflected away from the transducer and not returning to the transducer because of the angle of incidence (e.g., the angle is less than 90 degrees). One of the techniques (maneuvers) that can be used to increase needle visibility in the ultrasound is to move the transducer (probe) towards the needle tip and then away from the needle tip (i.e., the transducer can be pivoted while positioned on the body). This movement determines whether any observed spot on an ultrasound is a shaft or the tip of the needle.
There is therefore a need for a simple, effective method for tracking the needle as it is advanced in the body towards the target tissue.